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AMHERST, Mass. – The National Cancer Institute recently awarded a team led by epidemiologist Katherine Reeves of the University of Massachusetts Amherst School of Public Health and Health Sciences, a two-year, $177,373 grant to investigate, for the first time, possible connections between depression, antidepressant use and breast cancer.

Reeves, who is particularly interested in studying modifiable risk factors for breast cancer such as environmental contaminants, obesity, and exercise or lack of it, points out that antidepressants, once uncommon, are now the leading prescription drug taken by adults 18 to 44 years old, and the third most common drugs taken among all age groups.

“Fifty years ago these drugs were not common at all, but since the 1990s their use has increased significantly,” she says. “Some studies suggest that the type known as selective serotonin reuptake inhibitors (SSRI) may increase prolactin levels, which has been implicated in increased risk of breast cancer. So these drugs might be increasing breast cancer risk. It’s very important for the millions of women who take these medications that we have a better understanding of whether they affect breast health.” Prolactin is a hormone secreted by the pituitary gland and is involved in ovulation and nursing, for example, and plays a role in regulating the immune system.

There have been studies examining the relationship between depression and breast cancer risk, the epidemiologist says, but it’s not clear from those findings whether it’s the depression or the drugs that are associated with increased risk.

To explore that specific question, Reeves and fellow epidemiologist Sue Hankinson and biostatistician Jing Qian at UMass Amherst, with geriatric psychiatrist Olivia Okereke at Boston’s Brigham and Women’s Hospital, will analyze data on nearly 200,000 women enrolled in the Harvard Nurses Health Study (NHS) and NHS2, of whom 7,500 have been diagnosed with breast cancer.

Their aims are not only to investigate the effects of antidepressant use on breast cancer risk, but to assess whether depression increases breast cancer risk independent of antidepressant use and the impact of antidepressants on levels of circulating prolactin.

Reeves expects the risks to pre- and post-menopausal women may be different, for example.She says,“If we find that antidepressant use increases breast cancer risk for some women, it means they and their doctors can consider other options. Our hope is that the information from this study will help women make informed decisions about treating depression, especially for those already at increased risk of breast cancer for reasons such as family history.”